REVOLUTION
, in Geometry, the motion of rotation of a line about a fixed point or centre, or of any figure about a fixed axis, or upon any line or surface. Thus, the Revolution of a given line about a fixed centre, generates a circle; and that of a rightangled triangle about one side, as an axis, generates a cone; and that of a semicircle about its diameter, generates a sphere or globe, &c.
Revolution, in Astronomy, is the period of a star, planet, or comet, &c; or its course from any point of its orbit, till it return to the same again.
The planets have a twofold Revolution. The one about their own axis, usually called their diurnal rotation, which constitutes their day. The other about the sun, called their annual Revolution, or period, constituting their year.
